s12936-015-0789-x

Sylla et al. Malar J (2015) 14:275 DOI 10.1186/s12936-015-0789-x

RESEARCH

Sero-epidemiological evaluation ofPlasmodium falciparum malaria inSenegalKhadime Sylla1* , Roger Clment Kouly Tine1, Magatte Ndiaye1, Doudou Sow1, Assatou Sarr1, Marie Louise Tshibola Mbuyi2, Ibrahima Diouf1, Amy Col L1, Annie Abiola1, Mame Cheikh Seck1, Mouhamadou Ndiaye1, Ada Sadikh Badiane1, Jean Louis A NDiaye1, Daouda Ndiaye1, Oumar Faye1, Thrse Dieng1, Ymou Dieng1, Oumar Ndir1, Oumar Gaye1 and Babacar Faye1

Abstract Background: In Senegal, a significant decrease of malaria transmission intensity has been noted the last years. Parasitaemia has become lower and, therefore, more difficult to detect by microscopy. In the context of submicro-scopic parasitaemia, it has become relevant to rely on relevant malaria surveillance tools to better document malaria epidemiology in such settings. Serological markers have been proposed as an essential tool for malaria surveillance. This study aimed to evaluate the sero-epidemiological situation of Plasmodium falciparum malaria in two sentinel sites in Senegal.

Methods: Cross-sectional surveys were carried out in Velingara (south Senegal) and Keur Soce (central Senegal) between September and October 2010. Children under 10 years old, living in these areas, were enrolled using two-level, random sampling methods. P. falciparum infection was diagnosed using microscopy. P. falciparum antibod-ies against circumsporozoite protein (CSP), apical membrane protein (AMA1) and merozoite surface protein 1_42 (MSP1_42) were measured by ELISA method. A stepwise logistic regression analysis was done to assess factors associ-ated with P. falciparum antibodies carriage.

Results: A total of 1,865 children under 10 years old were enrolled. The overall falciparum malaria prevalence was 4.99% with high prevalence in Velingara of 10.03% compared to Keur Soce of 0.3%. Symptomatic malaria cases (fever associated with parasitaemia) represented 17.37%. Seroprevalence of anti-AMA1, anti-MSP1_42 and anti-CSP antibody was 38.12, 41.55 and 40.38%, respectively. The seroprevalence was more important in Velingara and increased with age, active malaria infection and area of residence.

Conclusion: The use of serological markers can contribute to improved malaria surveillance in areas with declining malaria transmission. This study provided useful baseline information about the sero-epidemiological situation of malaria in Senegal and can contribute to the identification of malaria hot spots in order to concentrate intervention efforts.

Trial registration number: PACTR201305000551876 (http://www.pactr.org).

Keywords: Malaria, Plasmodium falciparum, Serology, Epidemiology, Senegal

2015 Sylla et al. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

BackgroundDespite increasing efforts to control malaria and many African countries reporting a decrease of malaria burden

in recent years, the disease is still a major public health problem in many sub-Saharan African countries. Accord-ing to the World Health Organization, there were an estimated 207 million malaria cases and 627,000 malaria deaths in the world in 2012. This situation justifies the need to strengthen malaria control strategies including: (1) clinical case management of malaria cases using rapid diagnostic test (RDTs) and artemisinin combination

Open Access

*Correspondence: [email protected] 1 Service de Parasitologie-Mycologie, Facult de Mdecine, Pharmacie et Odontologie, Universit Cheikh Anta Diop de Dakar, Dakar, SngalFull list of author information is available at the end of the article

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therapy (ACT); (2) universal coverage of long-lasting, insecticide-treated nets (LLINs); (3) indoor residual spraying (IRS); and, (4) intermittent preventive treatment [13]. In Senegal, the National Malaria Control Pro-gramme (NMCP) initiated the scaling-up of malaria con-trol measures in 2005. Significant reduction of malaria morbidity has been noted these last years from 35.72% in 2001 to 5.62% in 2008 and 3.07% in 2009 [4]. Malaria parasitaemia has become lower and therefore more diffi-cult to detect by microscopy with an increase in the pro-portion of individuals carrying submicroscopic malaria parasites [5]. This may induce some limitation in malaria surveillance using microscopy. To overcome this issue, there is a need to develop innovative malaria surveillance tools that are more sensitive and more reliable for better documentation of malaria epidemiology. For this pur-pose, serology is proposed as a reliable and sensitive tool to assess malaria epidemiology as well as malaria inter-vention impact on malaria burden and transmission [68]. Several Plasmodium falciparum antigens have been studied to assess malaria transmission and impact on the host immunity. To assess the level of malaria transmis-sion, a pre-erythrocytic-stage antigen most commonly used is the circumsporozoite protein (CSP) with a short estimated half-life. Antibodies against this protein are correlated to transmission intensity and exposure dura-tion, but not necessarily to plasmodial infections. This protein is labile and disappears quickly in the absence of exposure. P. falciparum erythrocytic-stage antigens, such as merozoite surface protein 1 (MSP) and apical mem-brane antigen (AMA1) with long half-lives, reflect the cumulative exposure to malaria and can be used as an indicator of the burden of malaria [6, 7].

The analysis of immune responses against pre-erythro-cytic-stage antigen (CSP) and erythrocytic-stage antigens (MSP and AMA1) can contribute to assess malaria trans-mission and the impact on host immunity. This study was conducted to evaluate the sero-epidemiological situation of falciparum malaria using CSP, AMA1 and MSP1_42 in the context of scaling anti-malarial interventions in Senegal.

MethodsStudy areaThis study was carried out in two health districts (Velin-gara and NDoffane) with a different endemicity level. Velingara health district is located in the southeastern part of Senegal, 500km from the capital city of Dakar. In this district the study was conducted in Bonconto health post, which is headed by a nurse and has eight functional health huts staffed with community health workers,

serving a population of 10,016 inhabitants. Ndoffane is located in the central part of Senegal, 200 km from Dakar. In this district the study was conducted in Lamar-ame health post. This health post is led by a nurse and comprises 49 functional health huts and serves a popu-lation of 20,000 inhabitants. In both study areas malaria transmission is seasonal, occurring during the rainy season (from July to November) with a peak in between October to November. P. falciparum is the most predom-inant parasite species. These two areas are part of NMCP sentinel sites. Malaria control strategies implemented by the NMCP in both sites were represented by the case management of uncomplicated malaria cases using rapid diagnostic tests (RDTs) and artemisinin combina-tion therapy (ACT); intermittent preventive treatment in pregnant women; universal coverage of LLINs. The IRS is applied only in Velingara.

Study design andpopulationA cross-sectional survey was conducted in Velingara and Keur Soce in September and October 2010, several years after the implementation of malaria control measures. Children under 10 years old, living in the area or who stayed at the site for at least 6 months and whose par-ents or legal representatives gave informed consent form approval, were enrolled in the study using a two-level, random sampling method. Subjects whose parents or legal representatives did not give informed consent were excluded from the study.

Data collection methodAn informed consent questionnaire was administered to collect individual data on socio-demographic (age, gender, weight, height, area of residence, bed net use). Weight and height were collected to determine nutri-tional status. In addition, axillary temperature was measured.

Laboratory methodsParasitological assessmentFor each enrolled participant, three drops of blood were collected for thick and thin smear tests for the detec-tion of malaria prevalence using microscopy. Slides were stained for 15min with a 10% Giemsa solution. Parasite density was evaluated by counting the number of asexual parasites per 200 white blood cells (WBCs) and estimated by number of parasite per l using the following formula: number of parasites8,000/200 assuming a WBC count 8,000cells/l. Thick and thin smears were considered as negative after 100-field microscopic reading without any parasites being detected.

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Serological assessmentMalaria antigensApical membrane antigen (AMA1) was from the Pichia pastoris expressed ectodomain of P. falciparum FVO strain comprised amino acids 25545 [9] (Donated by DrDaniel Dodo, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana).

MSP1_42 protein was from the C-terminal MSP1_42 amino acid sequence of the Uganda-Palo Alto (FUP) P. falciparum isolate (GenBank Accession No. M37213) expressed in Escherichia coli (Ec) system. The recombi-nant protein, EcMSP1_42-FUP (Uganda-Palo Alto strain), represents the 33kDa fragment from the 3D7 P. falcipa-rum variant and the E-K-NG point mutations identified in the 19kDa fragment within the MSP1_42 native mol-ecule [10].

CSP was a full-length protein expressed in an Escheri-chia coli system containing amino-acids Leu19 to Ser411 (Indian isolate, GenBankTM No: AAN87606) [11].

MSP1_42 and CPS were donated by Dr Patrick Duffy and Dr Richard Shimp from NIH/NIAID (National Insti-tutes of Health/National Institute of Allergy and Infec-tious Diseases).

Enzymelinked immunosorbent assay (ELISA)Three drops of blood were collected onto Whatman 3MM filter paper, which was sealed and stored dry with desiccant at room temperature. Reconstituted sera were obtained from filter paper bloods spots described pre-viously [12, 13]. Sera were tested for anti-MSP1_42 IgG antibodies, anti-AMA1 IgG antibodies and anti-CSP antibodies by indirect ELISA. Samples were also tested on freeze thawed P. falciparum schizont extract (con-centration of 1108/ml), which was coated onto ELISA plates at 1/500.

Briefly, 96 well ELISA plates were coated with 100l/well of 0.1l/well of MSP1_42 and CSP antigens and 0.026 l/well of AMA1 in coating buffer (1.59 g Na2CO3, 2.93 g NaHCO3, 1 liter distilled water, pH 9.4). The plates were incubated overnight at 4C. After incubation, plates were washed at three times using PBS (5.7 g NaH2PO4, 16.7 g Na2HPO4, 85 g NaCl in 1 l distilled water) plus 0.05% Tween 20 (PBS/T) and blocked with 1% (w/v) skimmed milk power in PBS/T for 1 h at 37C. Eluates were removed from 4C just before use. After three more washes, eluates were diluted at a ration 1/100 in PBS/T and added 200l in duplicate in a well plate.

For each plate three types of control were used: deep well without serum but with a second antibody to meas-ure the non-specific binding, pool of sera from patients with P. falciparum malaria (positive control) and pool of sera from non-infected subjects (negative control) from

Copenhagen. Three washes were performed before incu-bation for 1h at 37 with secondary antibody (100l of horseradish peroxidase-conjugated rabbit anti-human IgG, SouthernBiotech ). After incubation for 1 h at 37C, plates were developed with TMB/E (Upstate, Chemicon et Linco, Millipore) as substrate for 30min at room temperature in the absence of light and the reac-tion was stopped by the addition of 50 l/well of 2 M H2SO4. Optical density was read at 450 nm against a 620nm with an ELISA TECAN SUNRISE reader.

Haematological assessmentOne drop of blood was collected from all participants for haemoglobin (Hb) level measurement using Hemo-Cue machine (HemoCue Hb 301). Anaemia was defined as Hb concentration below 11g/dl.

Statistical methodsAfter data collection, date entry work was performed using Excel software. Thereafter, analysis was carried out using Stata software version IC 12 software.

For serological assessment, the optical density was obtained by subtracting the average OD (Optical density) of duplicate wells from that of the corresponding blank wells. Values were converted into arbitrary units (AUs), as follows [14]:

To assess the nutritional status, data were transferred into Epi Info 3.04 d. The Z-scores for weight-for-age (underweight) and height-forage (stunting) were derived using Epinut Anthropometry. Children with Z-scores below2 standard deviation (SD) of the National Cen-tre for Health Statistic (NCHS), United States reference population median were considered to be malnourished.

Quantitative variables were described in terms of means, SD. Inter-group comparisons were done using ANOVA test or Student t test where appropriate, oth-erwise non-parametric tests such as MannWhitney or KruskalWallis were used.

For descriptive data, percentage was used to each out-come. Antibodies seroprevalence was calculated and expressed by percentage with their 95% confidence inter-vals. Proportions were compared using Chi square test or the Fisher exact test (univariate analysis). A stepwise logistic regression analysis was done to assess factors associated with P. falciparum antibodies carriage. Signifi-cance level of the different tests was set at 5%.

Ethical considerationsThe study was nested into a cluster-randomized trial [15] which had been approved by the Senegalese

AU = 100

[Ln(OD test sample) Ln(OD negative control)

Ln(OD positive control) Ln(OD negative control)

]

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National Ethical Committee (Conseil National dEthique et de Recherche en Sant) and registered at the Pan African Clinical Trial Registry: registration num-ber: PACTR201305000551876. In the field, individual informed consent was required prior to each participant enrolment. Community sensitization was done prior to the study to explain the planned investigations.

ResultsStudy participant characteristicsA total of 1,865 participants were studied (866 from Velingara and 999 from Keur Soce). The mean age of the study population was 4.242years. The study popula-tion was mainly represented by children under 5 years old (53.62%). A proportion of 7.83% were less than 1year old. Children over 5 years represented 38.55%. The sex ratio was 1.03. The mean Hb level was 9.93 3.3 g/dl and was lower in Velingara (8.5 3.4g/dl). The overall prevalence of anaemia (Hb

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value= 0.8] in children under 5 years old while it was more important in children over 5 years old 47.57% [ORa=1.28; IC (0.871.87), p value=0.43].

For children with malaria infection, the seroprevalence of anti-MSP1_42 antibody was 52.69% [ORa = 1.01; IC (0.651.55); p value = 0.95]. For children over 5 years, the seroprevalence of anti-CSP antibody was 43.53% [ORa = 1.08; IC (0.751.56); p = 0.66] compared to other children. Anti-CSP antibody was more important in female children (41%), children with stunting 43.72% [ORa=1.09; IC (0.851.4); p=0.45] and children with anaemia (40.44%). The prevalence of anti-CSP antibody was associated with active malaria infection. Prevalence of anti-CSP antibody was more important in children with malaria infection 46.24% [ORa=1.2; IC (0.781.84); p=0.4]. The prevalence of anti-CSP antibody was more important in Velingara 52.66% [ORa = 2.63; IC (2.133.24); p

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are consistent with results from national malaria indica-tor surveys conducted 20082009, which showed similar patterns in terms of P. falciparum carriage and anaemia prevalence [20]. The national survey conducted in 2012 and 2013 showed an overall prevalence of P. falciparum at 2.8% with disparities between the southern part (9.3%) and the central part (2.2%) of the country [21]. The dif-ference in malaria prevalence between the two areas demonstrates once again the heterogeneity of malaria transmission in Senegal. This was demonstrated in Gam-bia in 2008 and 2009 [22].

Similar results were found in 2005 with the heteroge-neity of malaria in the east and west of Cambodia [23]. Despite the low prevalence of P. falciparum, anaemia was closely associated with malaria parasitaemia. Other stud-ies demonstrated that the main factors influencing anae-mia occurrence in the central and the southern parts of the country are mainly represented by P. falciparum carriage, malnutrition, sickle cell traits and alpha-thalassaemia [24].

The overall seroprevalence of AMA1, MSP1_42 and CSP antibodies was 38.12, 41.55 and 40.38%, respectively. Sig-nificant difference between the two areas was observed with a higher seroprevalence in the southern part (Velin-gara). Although the serological assessment confirmed malaria heterogeneity as shown by microscopy. Propor-tion of P. falciparum carriage was significantly lower than antibodies level. These findings are in accordance with what were observed in Madagascar [6]. In Tanzania, similar results were noted with a high seroprevalence of antibodies against AMA1 (40.7%) and MSP1 (64.1%) [19]. Similar results were found in Ghana with high seropreva-lence of AMA1 and CSP antibodies [25]. A high preva-lence of PfMSP1 and PfAMA1 antibodies was found in Indonesia whatever the area and the season [26].

These results show that serology could be a good indicator for malaria surveillance. 5% of the total study participant was found positive by microscopy while anti-bodies excretion increased by at least sixfolds. The study demonstrated that using microscopy alone for malaria surveillance could underestimate malaria burden, par-ticularly in areas with reduced malaria transmission. These data are confirmed by other studies [6, 19, 23, 27].

The study showed that seroprevalence of AMA1, MSP1_42 and CSP antibodies increased with age, P. falciparum carriage and the area of residence. Similar results were found in Vanuatu in 2008 and in northern Peru between 2008 and 2010 [28, 29]. In 2002, a study in Ghana showed that the level of antibody was higher among older subjects [30]. This was also demonstrated in The Gambia and Senegal in 2002 [22, 31]. In chil-dren with P. falciparum infection, the seroprevalence of antibodies is higher compared to those without P. falci-parum infection. The association between malaria and

Table 5 Factors influencing the seroprevalence of anti-MSP1_42 antibodies

Number (%)

OR (95% CI)

ORa (95% CI)

p value

Age group (year)

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level of antibody (anti-AMA1, anti-MSP1_42 and anti-CSP) has been demonstrated by several immuno-epide-miological studies [3239]. Comparing both sites, the seroprevalence of antibodies is higher in Velingara than in Keur Soce. This may be due to the fact that malaria transmission is most intense in southern Senegal. The variation of malaria between areas has been demon-strated [22].

Gender, Hb level and nutritional status did not play a role in antibody production. This was demonstrated in 2002 in Senegalese preschool children when assessing the immunological consequences of intermittent preventive treatment [30].

Serological markers can be a useful tool for malaria epidemiology characterization particularly in areas with a decrease of malaria and can even contribute to the identification of malaria hot spots in order to con-centrate intervention efforts. Others studies suggest that sero-epidemiological analysis will be useful tool in assessing short-term changes in exposure and malaria transmission in area with a low or seasonal transmission. It was demonstrated in Ghana, Kenya and Indonesia [40, 41].

Study limitationThe age of the study population being limited to 10years constituted a study limitation. To better document the changing profile of malaria epidemiology, it would be rel-evant to extend the study to the other age groups in order to characterize the burden of the disease in the study areas.

ConclusionSerological markers can be used as complementary tools for malaria survey in areas with a declining pattern of malaria in Senegal. This study provided useful baseline information about the sero-epidemiological situation of malaria in Senegal and can contribute to the identifica-tion of malaria hot spots in order to concentrate inter-vention efforts.

Authors contributionsKS, RCT, MN, DS, AS, MLT, ID, ACL, AA, MCS, MN, ASB, JLN, DN, OF, TD, YD, ON, OG, and BF conceived and designed the study. KS and RCT monitored the data collection. KS, MN, AS, and MLT collected data in the site. KS analysed the data and wrote the first draft of the manuscript. All authors read and approved the final manuscript.

Author details1 Service de Parasitologie-Mycologie, Facult de Mdecine, Pharmacie et Odon-tologie, Universit Cheikh Anta Diop de Dakar, Dakar, Sngal. 2 Dpartement de Parasitologie-Mycologie, Universit des Sciences de la Sant, Libreville, Gabon.

AcknowledgementsWe thank all patients who agreed to participate in the study. We also acknowledge Dr Patrick Duffy and Dr Richard Shimp from NIH/NIAID (National

Institutes of Health/Nantional Institue of Allergy and Infectious Diseases) and Daniel Dodo, from Noguchi Memorial Institute for Medical Research, Univer-sity of Ghana, Legon, Ghana) who provided the antigens.

Compliance with ethical guidelines

Competing interestsThe authors declare that they have no competing interests.

Received: 30 January 2015 Accepted: 1 July 2015

References 1. WHO (2008) Global malaria control and elimination. Technical Consulta-

tion Report. Geneva, World Health Organization. http://www.who.int/malaria/publications/atoz/9789241596817/en/

2. WHO (2007) Malaria elimination: A field manual for low and moderate endemic countries. Geneva, World Health Organization. www.who.int/entity/malaria/publications/atoz/9789241596084

3. WHO (2010) WHO Policy recommendation on Intermittent Preventive Treatment during infancy with sulphadoxine-pyrimethamine (SP-IPTi) for Plasmodium falciparum malaria control in Africa. Geneva, World Health Organization. http://www.who.int/malaria/news/WHO_policy_recom-mendation_IPTi_032010.pdf?ua=1

4. National malaria control program Senegal (2006) Strategic plan against malaria 20062010. http://www.pnlp.sn/rapport.html

5. Mwingira F, Genton B, Kabanywanyi AN, Felger I (2014) Comparison of detection methods to estimate asexual Plasmodium falciparum parasite prevalence and gametocyte carriage in a community survey in Tanzania. Malar J 13:433

6. Razakandrainibe R, Thonier V, Ratsimbasoa A, Rakotomalala E, Ravaoari-soa E, Raherinjafy R et al (2009) Epidemiological situation of malaria in Madagascar: baseline data for monitoring the impact of malaria control programs using serological markers. Acta Trop 111:160167

7. Rogier C, Henry MC, Trape JF (2009) Evaluation pidmiologique du paludisme en zone dendmie. Med Trop 69:123124

8. Rogier C (2003) Paludisme de lenfant en zone dendmie : Epidmiologie, Acquisition dune immunit et Stratgies de lutte. Med Trop 63:449464

9. Kocken CH, Withers-Martinez C, Dubbeld MA, Van Der WA, Hackett F, Val-derrama A et al (2002) High-level expression of the malaria blood-stage vaccine candidate Plasmodium falciparum apical membrane antigen 1 and induction of antibodies that inhibit erythrocyte invasion. Infect Immun 70:44714476

10. Shimp RL, Martin LB, Zhang Y, Henderson BS, Duggan P et al (2006) Production and characterization of clinical grade Escherichia coli-derived Plasmodium falciparum 42-kDa merozoite surface protein 1 (MSP142) in the absence of an affinity tag. Protein Expr Purif 50:5867

11. Plassmeyer ML, Reiter K, Shimp RL, Kotova S, Smith PD, Hurt DE et al (2009) Structure of the Plasmodium falciparum circumsporozoite protein, a leading malaria vaccine candidate. J Biol Chem 284: 2695126963

12. Corran PH, Cook J, Lynch C, Leendertse H, Manjurano A, Griffin J et al (2008) Dried blood spots as a source of anti-malarial antibodies for epide-miological studies. Malar J 7:195

13. Drakeley CJ, Corran PH, Coleman PG, Tongren JE, McDonald SL, Carneiro I et al (2005) Estimating medium- and long-term trends in malaria trans-mission by using serological markers of malaria exposure. Proc Natl Acad Sci USA 102:51085113

14. Guitard J, Cottrell G, Magnouha NM, Salanti A, Li T, Sow S et al (2008) Differential evolution of anti-VAR2CSA- IgG3 in primigravidae and mul-tigravidae pregnant women infected by Plasmodium falciparum. Malar J 7:10

15. Tine RC, Faye B, Ndour CT, Ndiaye JL, Ndiaye M, Bassene C et al (2011) Impact of combining intermittent preventive treatment with home management of malaria in children less than 10 years in a rural area of Senegal: a cluster randomized trial. Malar J 10:358

16. Dolgin E (2010) Targeting hotspots of transmission promises to reduce malaria. Nat Med 16:1055

Page 8 of 8Sylla et al. Malar J (2015) 14:275

17. Woolhouse ME, Dye C, Etard JF, Smith T, Charlwood JD, Garnett GP et al (1997) Heterogeneities in the transmission of infectious agents: implications for the design of control programs. Proc Natl Acad Sci USA 94:338342

18. Oduro AR, Bojang KA, Conway DJ, Corrah T, Greenwood BM, Schellenberg D (2011) Health centre surveys as a potential tool for monitoring malaria epidemiology by area and over time. Plos One 6:26305

19. Stewart L, Gosling R, Griffin J, Gesase S, Campo J, Hashim R et al (2009) Rapid assessment of malaria transmission using age-specific sero-conver-sion rates. Plos One 4:6083

20. Agence Nationale de la Statistique et de la Dmographie (ANSD), Sngal. Enqute nationale sur le paludisme 20082009 Juillet 2009. http://www.ansd.sn/ressources/rapports/EDS-continue_2008-2009.pdf

21. Agence Nationale de la Statistique et de la Dmographie (ANSD), Sn-gal. Enqute Dmographique et de Sant Continue au Sngal 20122013. http://www.ansd.sn/ressources/rapports/EDS-continue_2012-2013.pdf

22. Oduro RA, Conway DJ, Schellenberg D, Satoguina J, Greenwood BM and Bojang KA (2013) Sero-epidemiological and parasitological evaluation of the heterogeneity of malaria infection in the Gambia. Malar J 12:222

23. Cook J, Speybroeck N, Sochanta T, Somony H, Sokny M, Filip Claes F et al. (2012) Sero epidemiological evaluation of changes in Plasmodium falcipa-rum and Plasmodium vivax transmission patterns over the rainy season in Cambodia. Malar J 11:86

24. Tine RT, Ndiaye M, Hansson HH, Ndour CT, Faye B, Alifrangis M et al (2012) The association between malaria parasitaemia, erythrocyte polymor-phisms, malnutrition and anaemia in children less than 10 years in Senegal: a case control study. BMC Res Notes 5:565

25. Kwadwo AK, Samuel B, Daniel D, Eric KB, Emmanuel KD, Daniel M et al (2014) Anti-sporozoite antibodies as alternative markers for malaria transmission intensity estimation. Malar J 13:103

26. Supargiyono S, Bretscher MT, Wijayanti MA, Sutanto I, Nugraheni D, Rozqie R et al (2013) Seasonal changes in the antibody responses against Plasmodium falciparum merozoite surface antigens in areas of differing malaria endemicity in Indonesia. Malar J 12:444

27. Cook J, Reid H, Iavro J, Kuwahata M, Taleo G, Clements A et al (2010) Using serological measures to monitor changes in malaria transmission in Vanuatu. Malar J 9:169

28. Aguirre A, Lianos CA, Cook J, Contreras MJ, Soto V, Gamboa D et al (2013) Assessing malaria transmission in a low endemiciy area of north-western Peru. Malar J 12:339

29. Dodoo D, Aikins A, Kusi KA, Lamptey H, Remarque E, Milligan P et al (2008) Cohort study of the association of antibody levels to AMA1, MSP1_19, MSP3 and GLURP with protection from clinical malaria in Ghanaian children. Malar J 7:142

30. Boulanger D, Sarr JB, Fillol F, Sokhna C, Cisse B, Schacht A.M et al. (2010) Immunological consequences of intermittent preventive treatment against malaria in Senegalese preschool children. Malar J 9:363

31. Braga EM, Barros RM, Reis TA, Fontes CJ, Morais CG, Martins MS et al (2002) Association of the IgG response to Plasmodium falciparum mero-zoite protein (C-terminal 19 kD) with clinical immunity to malaria in the Brazilian Amazon region. Am J Trop Med Hyg 66:461466

32. Holder AA, Riley EM (1996) Clinical immunity to Plasmodium falciparum malaria is associated with serum antibodies to the 19-kDa C-terminal fragment of the merozoite surface antigen, PfMSP-1. J Infect Dis 173:765769

33. Kitua AY, Lemnge MM, Theander TG (2005) Cytophilic antibodies to Plas-modium falciparum glutamate rich protein are associated with malaria protection in an area of holoendemic transmission. Malar J 4:48

34. Meraldi V, Nebie I, Tiono AB, Diallo D, Sanogo E, Theisen M et al (2004) Natural antibody response to Plasmodium falciparum Exp-1, MSP-3 and GLURP long synthetic peptides and association with protection. Parasite Immunol 26:265272

35. Dodoo D, Theisen M, Kurtzhals JA, Akanmori BD, Koram KA, Jepsen S et al (2000) Naturally acquired antibodies to the glutamate-rich protein are associated with protection against Plasmodium falciparum malaria. J Infect Dis 181:12021205

36. Theisen M, Dodoo D, Toure Balde A, Soe S, Corradin G, Koram KK et al (2001) Selection of glutamate-rich protein long synthetic peptides for vaccine development: antigenicity and relationship with clinical protec-tion and immunogenicity. Infect Immun 69:52235229

37. Oeuvray C, Theisen M, Rogier C, Trape JF, Jepsen S, Druilhe P (2000) Cyt-ophilic immunoglobulin responses to Plasmodium falciparum glutamate-rich protein are correlated with protection against clinical malaria in Dielmo, Senegal. Infect Immun 68:26172620

38. Nahlen BL, Bloland PB, Kaslow DC, Lal AA (1998) A longitudinal inves-tigation of IgG and IgM antibody responses to the merozoite surface protein-1 19-kiloDalton domain of Plasmodium falciparum in pregnant women and infants: associations with febrile illness, parasitemia, and anemia. Am J Trop Med Hyg 58:211219

39. Morais CG, Soares IS, Carvalho LH, Fontes CJ, Krettli AU, Braga EM (2005) IgG isotype to C-terminal 19 kDa of Plasmodium vivax merozoite surface protein 1 among subjects with different levels of exposure to malaria in Brazil. Parasitol Res 95:420426

40. Bretscher MT, Supargiyono S, Wijayanti MA, Nugraheni D, Widyastuti AN, Lobo NF et al (2013) Measurement of Plasmodium falciparum transmis-sion intensity using serological cohort data from Indonesian schoolchil-dren. Malar J 12:21

41. Jacklyn W, Hamel MJ, Drakeley CJ, Kariuki S, Shi Y, Lal A et al (2014) Sero-logical markers for monitoring historical changes in malaria transmission intensity in a highly endemic region of Western Kenya, 19942009. Malar J 13:451

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Sero-epidemiological evaluation ofPlasmodium falciparum malaria inSenegalAbstract Background: Methods: Results: Conclusion:

BackgroundMethodsStudy areaStudy design andpopulationData collection method

Laboratory methodsParasitological assessment

Serological assessmentMalaria antigensEnzyme-linked immunosorbent assay (ELISA)Haematological assessmentStatistical methodsEthical considerations

ResultsStudy participant characteristicsMalariaometric indices

DiscussionStudy limitation

ConclusionAuthors contributionsReceived: 30 January 2015 Accepted: 1 July 2015References